/*
 * Copyright (c) 2007-2012, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */
package com.sun.org.apache.bcel.internal.classfile;

/* ====================================================================
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 2001 The Apache Software Foundation.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Apache" and "Apache Software Foundation" and
 *    "Apache BCEL" must not be used to endorse or promote products
 *    derived from this software without prior written permission. For
 *    written permission, please contact apache@apache.org.
 *
 * 5. Products derived from this software may not be called "Apache",
 *    "Apache BCEL", nor may "Apache" appear in their name, without
 *    prior written permission of the Apache Software Foundation.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 */

import com.sun.org.apache.bcel.internal.Constants;
import java.io.*;

/**
 * Abstract superclass for classes to represent the different constant types
 * in the constant pool of a class file. The classes keep closely to
 * the JVM specification.
 *
 * @author  <A HREF="mailto:markus.dahm@berlin.de">M. Dahm</A>
 */
public abstract class Constant implements Cloneable, Node, Serializable {
    /* In fact this tag is redundant since we can distinguish different
     * `Constant' objects by their type, i.e., via `instanceof'. In some
     * places we will use the tag for switch()es anyway.
     *
     * First, we want match the specification as closely as possible. Second we
     * need the tag as an index to select the corresponding class name from the
     * `CONSTANT_NAMES' array.
     */
    protected byte tag;

    Constant(byte tag) {
        this.tag = tag;
    }

    /**
     * Called by objects that are traversing the nodes of the tree implicitely
     * defined by the contents of a Java class. I.e., the hierarchy of methods,
     * fields, attributes, etc. spawns a tree of objects.
     *
     * @param v Visitor object
     */
    public abstract void accept(Visitor v);

    public abstract void dump(DataOutputStream file) throws IOException;

    /**
     * @return Tag of constant, i.e., its type. No setTag() method to avoid
     * confusion.
     */
    public final byte getTag() {
        return tag;
    }

    /**
     * @return String representation.
     */
    public String toString() {
        return Constants.CONSTANT_NAMES[tag] + "[" + tag + "]";
    }

    /**
     * @return deep copy of this constant
     */
    public Constant copy() {
        try {
            return (Constant) super.clone();
        } catch (CloneNotSupportedException e) {
        }

        return null;
    }

    public Object clone() throws CloneNotSupportedException {
        return super.clone();
    }

    /**
     * Read one constant from the given file, the type depends on a tag byte.
     *
     * @param file Input stream
     * @return Constant object
     */
    static final Constant readConstant(DataInputStream file) throws IOException, ClassFormatException {
        byte b = file.readByte(); // Read tag byte

        switch (b) {
            case Constants.CONSTANT_Class:
                return new ConstantClass(file);
            case Constants.CONSTANT_Fieldref:
                return new ConstantFieldref(file);
            case Constants.CONSTANT_Methodref:
                return new ConstantMethodref(file);
            case Constants.CONSTANT_InterfaceMethodref:
                return new ConstantInterfaceMethodref(file);
            case Constants.CONSTANT_String:
                return new ConstantString(file);
            case Constants.CONSTANT_Integer:
                return new ConstantInteger(file);
            case Constants.CONSTANT_Float:
                return new ConstantFloat(file);
            case Constants.CONSTANT_Long:
                return new ConstantLong(file);
            case Constants.CONSTANT_Double:
                return new ConstantDouble(file);
            case Constants.CONSTANT_NameAndType:
                return new ConstantNameAndType(file);
            case Constants.CONSTANT_Utf8:
                return new ConstantUtf8(file);
            default:
                throw new ClassFormatException("Invalid byte tag in constant pool: " + b);
        }
    }
}
